TA has 2 meanings
People who include TA in a message may be saying "thanks again." This acronym is a quick way to thank someone who did something kind for you.
You're most likely to receive TA from someone who has already thanked you for something nice you did. TA is that person's (brief) way of re-expressing their gratitude, and letting you know they really did appreciate that thing you did for them. (No, really. They did!)
TA for having us over to dinner last night!
Loved having you! Let's do it again soon.
|kthxbai||OK, thanks, bye|
|T4T||Thanks for trade|
|TIA||Thanks in advance|
|YVW||You're very welcome|
In education, a TA is a "teaching assistant." While TA can refer to any sort of teaching assistant, it typically refers to a graduate student who assists a college professor with their teaching courseload.
TAs assist teachers by handling some classroom sessions, grading homework, tutoring students, and holding office hours. Often, TAs are themselves looking to become teachers - and working as a TA provides them with practice.